125-200cc WR125 sheared flywheel key

If you haven't already, you may want to check and make sure that your flywheel nut is properly torqued. I was riding today and my bike quit abruptly. I determined that it had no spark. I put in a call to my dealer, Ridersville in Berkley Springs, WV and spoke with Harold for a bit. He talked me through a few checks and then asked me if I had wrecked the bike any time recently. I was embarrassed to have to admit that I had pitched the poor thing a couple of times but nothing huge. He asked if I had hit any trees or had any abrupt stops. It was then that the now hazy memory of a recent hare scramble where I used a tree to turn my front fender inside out started coming back to me. He had me remove my flywheel cover and have my buddy kick it over. The shaft was turning and the wheel didn't move! Also, the nut was so loose that I could back it off with my fingers. What we don't know was if this was possibly an oversight by the factory or not. Harold told me that it is rare, but sometimes a hard hit or sudden stop can shear the key. I now have a puller and two keys on the way.

Had that happen to my '82 250WR.

Thanx for shearing, I mean sharing. I am going to check mine right away.

Mine was so tight that it took heat and some "Persuasion" taps from the dead blow hammer to get it loose.

Walt

OMFG !!

at least im not the only one thats had this happen! thanks for sharing Skoots!

Follow up

I called Ridersville and learned that my puller was on back order. I had them send the keys on anyway. If something is already falling off, it's fairly intuitive that you shouldn't need a special puller to remove it. I installed a new key and because I couldn't find any torque specs in the owner's manual I decided to torque the nut to 25 ft.lbs. The bike lit up on the first kick and I was feeling pretty smugten seconds and a few blips of the throttle later it died. A quick inspection confirmed that I had stripped half of my key supply (2) I called Harold and he told me that he had never heard of this happening with a 125 and suggested that I call George Earl of Up-tite and get his opinion. I had the good fortune of being able to reach Mr. Earl right away and he told me that I had a miss-fit. He explained to me how use lapping compound with the key removed and lap a perfect fit between the flywheel and the crankshaft. He also instructed me to torque the nut to 50 ft.lbs. It turns out that this was a common issue in the old days, but is rarely seen on modern bikes. In a rare instance of me actually following instructions, I performed the above mentioned procedure and once again the bike lit up on the first kickI ran it for a moment and stopped and checked the torque on the nut. It was fine and I replaced the cover and went for a little ride. So far, so good...tomorrow we head for the trails.

That's good news David glad you got her up and running again. Good luck with the trail ride tomorrow.

You healing up okay?

Been riding huskys for over 20 years NEVER have had it happen, but did see it happen to a 2000-2001 wr250. The guy stalled it real hard and thats what happened. I will take my chances with my wr125.

Apparently it is extremely rare. Which is good. I hope that I am done with it. Love the bike!

Yes thanks David getting a little better every day.

Hi All, I posted this issue last year as it happened to both of my son's 07 WR125's.
It actually happened to my oldest son twice, the second time as he was leading the 200 B class at the Hixton WI OMA race. He was also third overall B at the time.
He was not happy to say the least.
I did not realize that a sudden stop could cause this, but it makes sense.

A sudden stop shouldn't do this. The tapers (in the flywheel and on the crank) should provide such an interference fit that it should be a struggle to get the flywheel off - even with the correct puller.

The Woodruff key is there only for alignment. It is not designed to transmit torque.

On all the multitudes of knackered 2-strokes I've had over the last 25+ years I've never seen a flywheel nut come undone on it's own. However, it may conceivably work loose if the flywheel is not a secure fit on the crank taper.

Older bike riders may remember using a little fine lapping paste to bed tapered parts together. However, this shouldn't be necessary in the modern world.

Perhaps this could turn into a warranty thing?

The lapping trick seems to have done the job. Rode a 2 hr. hare scramble yesterday with no issues.

When my kid raced gokarts we didn't use flywheel keys. Offset keys
were available but it was kind of gray area with some tech. inspectors. So we used to leave them out and use lapping compound, then it was the inspectors fault for loosing the
key during tear down.